The Capricorn Eddy: a prominent driver of the ecology and future of the southern Great Barrier Reef

Abstract

This study focuses on a mesoscale eddy feature, the 'Capricorn Eddy', that typically forms within an indentation of the continental shelf in the southern GBR system. Satellite data at moderate resolution (1 km) are used to examine relevant mesoscale and sub-mesoscale sea surface dynamics. Available in situ measurements and model data are used to validate the satellite observations and to specify the nature of the processes occurring within the water column itself. The characteristic features are identified and physical theory employed to develop an understanding of associated processes. In particular, the effect of the eddy in raising cooler, nutrient-enriched oceanic subsurface water and transporting it to the reef zone, and eventually into the lagoon, is shown. This study demonstrates that the linkages between large-scale oceanography and the meso-and sub-mesoscale patterns are crucial to determining biologic responses on the scale of reef communities and may be key to understanding climate change impacts at the relevant spatial scales.

Wind Conditions on the Great Barrier Reef Influenced the Recruitment of Snapper (Lutjanus carponotatus)

“…Finally, to validate the simulation of the CE, we compared the currents simulated in scenario 2, which was forced with the CE and average wind, with ADCP measurements taken during identified eddy events. Weeks et al (2010) identified an eddy event which lasted for a least 9 days, from 27 September 2008 to 6 October 2008. Mao and Luick (2014) eddy event.…”

“…Increased productivity could have a trickle up affect whereby an increase in primary production boosts secondary production, increasing the abundance of the prey species targeted by the predatory L. carponotatus (Jennings et al, 2001). Multiple sources of upwelling have been identified in the southern GBR, including strong northerly winds and the Capricorn Eddy (CE; Weeks et al, 2010;Mao and Luick, 2014). Finally, when we correlated the prevalence of favorable winds with recruitment, we only considered winds, and therefore spawning, in the period of peak L. carponotatus production (October to January; Russell et al, 1977;Kritzer, 2004).…”

“…Sponaugle et al (2005) found that the arrival of multi-taxa larval pulses to reefs in the Florida Keys coincided with the passage of sub mesoscale eddies with diameters of 10 to 40 km, produced from the decay of larger mesoscale eddies 100-200 km in diameter. The little researched CE appears to have a diameter of approximately 100 km when present (Weeks et al, 2010;Mao and Luick, 2014). The CE may retain the larvae that it advects from reefs in the CBG, and from the Swain Reefs to the north of the CBG.…”

“…The complex oceanography of the region could potentially affect the strength of recruitment events. The Capricorn Eddy (CE), a large, transient mesoscale oceanic eddy, forms offshore of the CBG (Weeks et al, 2010;Mao and Luick, 2014). It is presumably ecologically important as it upwells cool nutrient rich water to the surface (Weeks et al, 2010) and mesoscale eddies can greatly influence the dispersal trajectories of fish larvae (Sponaugle et al, 2005).…”

“…The Capricorn Eddy (CE), a large, transient mesoscale oceanic eddy, forms offshore of the CBG (Weeks et al, 2010;Mao and Luick, 2014). It is presumably ecologically important as it upwells cool nutrient rich water to the surface (Weeks et al, 2010) and mesoscale eddies can greatly influence the dispersal trajectories of fish larvae (Sponaugle et al, 2005). Additionally, the CBG lies on a shallow section of the Australian continental shelf, and the surface currents in this region are largely wind driven (Andutta et al, 2013;Mao and Luick, 2014).…”